The present invention relates generally to apparatus for producing the upper part of a casting mold and more particularly to equipment which includes a feed hopper for delivering molding compound into a molding box within which the mold is formed. The equipment to which the present invention relates includes a presser board and a mold table between which the molds are compressed with a pattern plate being attached on the mold table and with a sink pattern member being arranged on the presser board for forming a sink in the mold. A sprue pattern member is also provided for forming a sprue in communication between the pattern means on the pattern plate and the sink of the mold.
Various molding devices have been used for forming in a mold feed uppers, casting stumps or sinks on the top of the upper part of the casting mold and also for forming associated sprues and spouts in the casting mold.
In the prior art, for example German Pat. No. 1,051,064, techniques are known for forming such sprue depressions in the mold forming material particularly in connection with fully automatic molding equipment. Examples of this type of prior art technique usually require a milling tool as well as an additional operation thereby giving rise to undesirable effects with regard to station time.
Further known prior art techniques, as disclosed for example in German Pat. No. 744,158, utilize sprue molding devices made of rubber which are attached upon a journal of the pattern plate prior to the commencement of molding operation. Such parts must be removed from the casting mold after it is formed and before it is lifted. In molding plants which are designed for continuous production, this type of sprue formation involves a disadvantageous loss of time and the risk that accidents might occur. Such disadvantages cannot be overlooked.
Additional prior art devices, known for example from German DAS No. 1,083,024, involve a molding body called an upper course pattern which is designed for molding a sink and the respective sprues. Several journals, used partly for molding the sprues and partly as a support for the molding body, are arranged perpendicularly to the molding plane in the upper course pattern. These are inserted in bores and they are susceptible to movement therein in the axial direction. Into such bores there is inserted a compression spring acting on the journals, with the spring being compressed during the final compression of the mold. The spring tends to lift the upper course pattern from the mold by virtue of a certain degree of expansion which occurs and in order to fix the position of the upper course pattern on the pattern plate, pilot bars are arranged on the pattern plate for engagement by the bottom ends of the journals. A specially designed device is used for the attachment of the upper course pattern on the pattern plate before the formation of the mold and for lifting it from the finished casting mold. This additional molding operation involving attachment and lifting of the upper course pattern as well as the maintenance of the required device, produce an adverse effect on the costs of mold production. Additionally, it is found that patterns cannot be arranged at those points of the pattern plate on which the supporting journals bear thereby further limiting the utilization of the pattern plate.
Other molding devices known from the prior art, for example, German DOS No. 2,245,169, involve a molding die for molding sprue recesses arranged on the underside of a presser board of the presser head and attachment on the pattern plate of several column-shaped pattern parts for forming molding sprues. Recesses corresponding to the column-shaped pattern parts are provided in the molding die into which the pattern parts penetrate during the pressing of the molding die into the molding compound. However, molding compound which adheres to the pattern parts is unavoidably pressed into the recesses of the molding die thereby giving rise to a requirement for additional cleaning operations and the likelihood of premature wear of the interlocking parts.
Additionally, as is known from existing molding technology, the molding compound tends to exhibit certain characteristics during its compression. In order to obtain a uniform compression of the molding compound, the pressure which is applied should be uniformly distributed over the entire mold surface. Such a requirement is not met, however, in many prior art techniques since the molding compound tends to be compressed more within the range of the molding die by the height of the latter thereby giving rise to an adverse effect upon the quality of the mold which is produced.
Accordingly, it is an object of the invention to provide a molding device for the production of the upper parts of casting molds which may be used on molding machines having feed hoppers which are swung over the mold table and attached to the mold box for delivering molding compound thereto and which operate in molding plants involving intermittent or continuous operation. The molding device of the invention is also intended for use with existing molding equipment without requiring additional costs with regard to the particular mold box forms which are used, and it is intended as capable of formation by simple means permitting conversion of the casting molds to different casting systems without the requirement of specially skilled operators.